A colder spark plug helps this because it pulls more heat into the head of the engine from the combustion chamber and is less likely to act as a point of ignition before it is triggered by the ECU. The knock sensors can’t pick up pre-ignition because pre-ignition happens when the air-fuel mixtures ignites BEFORE the spark event and will usually result in a hole in a piston or broken rod.

However it will reduce the CHANCE for pre-ignition and pre-ignition is much more serious than knock and more damaging should it occur. Replacing the spark plugs with a step colder will not prevent knock – knock is a result of fuel used, tune, and temperatures – and I mention this because we get asked all the time if replacing the plugs will reduce knock. Knock is caused by multiple flame fronts starting AFTER the initial flame front was started by the spark plug. Knock is what the knock sensor picks up and you can datalog this as ignition corrections during a pull. Because of this our red development MK7 GTI is getting a fresh set of plugs.ĭo not confuse pre-ignition and detonation (or knock). For more in-depth spark plug tech check out our spark plug article here. With more heat in the combustion chamber, you may start to move outside the optimal heat range of the OEM plugs and thus have an increased risk of pre-ignition. All you people who buy into that stuff have been SCAMMED.When turning up the power on a vehicle such as we are doing via the COBB Accessport, inevitably more heat is generated. Like the old school Splitfires, the gimmick plug that first conned the masses into thinking $6 instead of $1 spark plugs were good and now all plug maker CEOs worship at the altar of Splitfire every day saying.thank you for bumping our profits up 400%. Physics for other idiots if you will.their product is and always will be garbage. One controls combustion chamber temperatures by changing the heat radiation characteristics of the plug, NOT the temperature. ALL plugs 'burn' at the same temperature, rather they RADIATE or DISSIPATE the heat off differently. Pure 'i failed school, especially physics class' bullshit. 'Some spark plugs are made to burn hotter than others.' Read the last couple lines there, they refer you to STOCK plugs (owners' manual) and they (I assure you, I sold them) have no real provision for anything other than DEAD STOCK PLUGS. Do the same using a phone book - virtually no heat transfer, just as there's little through a LONG spark plug insulator. Touch an ice cube with a sheet of paper between it and your hand - feels cold right? That's heat transfer through a small insulator. The porcelain is the insulator (electrical & heat) between tip & plug shell, which screws into the head to transfer heat/electricity. The less insulation between the tip & the head the 'colder' the tip will stay. The cylinder head is the 'cold' part compared to the plug tip. Harder to explain this in words than pictures.

In either case, you can't tell heat range by looking at how long the tip is beyond the base - it's the distance from tip to where the porcelain touches the wall of the plug that counts. Extended tip style won't work when very 'cold' is needed, since the tip stands up beyond the base.

More likely to misfire if the engine designer wanted a plug that puts the spark further out. That recessed one would probably need to be a 'hotter' plug to avoid fouling when used in the same engine. if you put an extended tip in an engine that needs a short one, the piston would smash it. If those plugs are used in the same engine, one is wrong for the application.Įxtended tip works in a larger combustion chamber, the short 'flat' one works where there isn't room for an extended tip. If you ever see a VERY cold racing plug, there's almost no porcelain 'tip' at all - an almost flat porcelain between the electrode & the shell. A LONG insulator (as E3 mentioned obliquely) means the good insulation of that LONG path to the shell through the insulating porcelain will let the tip stay hot. The short path between the electrode tip & the plug shell (steel threaded part) of a short insulator gives the most cooling to the tip. Look up an explanation from NGK, Bosch, Champion - whoever you like to see a diagram & pictures to explain it better. E3's explanation is the most convoluted way to say the same thing I did I've ever seen.

Focus st cobb stage 1 colder plugs